Unicorn in the classroom—a student-led experiment on the speed of sound using Arduino

Abstract We aimed to familiarise students with the fundamentals of digital measurements early in their physics studies, as this can help maintain their interest and develop their digital competencies. Therefore, in the seventh grade, we used uniform motion—a well-known and easily understandable concept—to introduce this new measurement technique, combining digital tools with classical methods. We employed a simple, Arduino-controlled HC-SR04 ultrasonic sensor (easily assembled even at home) to determine the speed of sound in air and, if needed, in other media (e.g. carbon dioxide). A key advantage of this experiment is that the results can be directly compared to official reference values, providing students with immediate positive feedback on their work. The novelty of our developed tool lies in its cross-grade applicability and reusability, enabling the discussion of core physics concepts like systematic and statistical errors. As part of the project, we piloted the equipment and task sequence, collecting student feedback via questionnaires. Attitude survey results indicate that students found the experiment highly engaging, suggesting its potential to enhance classroom motivation and foster a positive attitude toward the subject.